Optical fiber having reduced dispersion

Abstract

Dispersion is reduced in a graded index optical fiber having a finite number of core layers by introducing slow longitudinal variations into the index of refraction of each layer. The index of refraction of each layer varies between a maximum which is proximate in value to the minimum index of refraction of the more central radially adjacent layer and a minimum which is proximate in value to the maximum index of refraction of the next furthermost radially adjacent layer.

What is claimed is: 
     
       1. A graded index optical fiber having decreased optical dispersion comprising a core member and a cladding surrounding said core member, said core member including a plurality of layers the refractive indices of which radially decrease from a maximum at the center of the fiber characterized in that the index of refraction of each of said layers has spatial fluctuations along the longitudinal axis of said fiber, the fluctuations in the refractive index of each layer occuring slowly, the minimum refractive index of each layer being proximate in value to the maximum index of the radially next furthermost adjacent layer, and the maximum refractive index of each layer being proximate in value to the minimum index of the radially more central adjacent layer.   
     
     
       2. A graded index optical fiber as defined in claim 1 further characterized in that the distance between maxima in the index of refraction of each layer is within the range of 0.1 meter to 400 meters. 
     
     
       3. A graded index optical fiber as defined in claim 2 further characterized in that the distance between maxima in the index of refraction of each layer is within the range of 10 meters to 100 meters. 
     
     
       4. A graded index optical fiber as defined in claim 1 further characterized in that said spatial fluctuations are periodic along the longitudinal axis of said fiber. 
     
     
       5. A graded index optical fiber as defined in claim 4 further characterized in that the period of said spatial fluctuations is equal in each layer. 
     
     
       6. A graded index optical fiber as defined in claim 5 further characterized in that the longitudinal spatial positions of the minima in the refractive index of each layer are proximate to the longitudinal spatial positions of the maxima in the refractive index of the adjacent layers.